线程----BlockingQueue (转)
import java.util.concurrent.ArrayBlockingQueue;
import java.util.concurrent.BlockingQueue;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
?
/**
??? 本例介紹一個特殊的隊列:BlockingQueue,如果BlockQueue是空的,從BlockingQueue取東西的操作將會被阻斷進入等待狀態,直到BlockingQueue進了東西才會被喚醒.同樣,如果BlockingQueue是滿的,任何試圖往里存東西的操作也會被阻斷進入等待狀態,直到BlockingQueue里有空間才會被喚醒繼續操作.
??? 本例再次實現11.4線程----條件Condition中介紹的籃子程序,不過這個籃子中最多能放的蘋果數不是1,可以隨意指定.當籃子滿時,生產者進入等待狀態,當籃子空時,消費者等待.
?*/
/**
??? 使用BlockingQueue的關鍵技術點如下:
??? 1.BlockingQueue定義的常用方法如下:
??? ??? 1)add(anObject):把anObject加到BlockingQueue里,即如果BlockingQueue可以容納,則返回true,否則招聘異常
??? ??? 2)offer(anObject):表示如果可能的話,將anObject加到BlockingQueue里,即如果BlockingQueue可以容納,則返回true,否則返回false.
??? ??? 3)put(anObject):把anObject加到BlockingQueue里,如果BlockQueue沒有空間,則調用此方法的線程被阻斷直到BlockingQueue里面有空間再繼續.
??? ??? 4)poll(time):取走BlockingQueue里排在首位的對象,若不能立即取出,則可以等time參數規定的時間,取不到時返回null
??? ??? 5)take():取走BlockingQueue里排在首位的對象,若BlockingQueue為空,阻斷進入等待狀態直到Blocking有新的對象被加入為止
??? 2.BlockingQueue有四個具體的實現類,根據不同需求,選擇不同的實現類
??????? 1)ArrayBlockingQueue:規定大小的BlockingQueue,其構造函數必須帶一個int參數來指明其大小.其所含的對象是以FIFO(先入先出)順序排序的.
??????? 2)LinkedBlockingQueue:大小不定的BlockingQueue,若其構造函數帶一個規定大小的參數,生成的BlockingQueue有大小限制,若不帶大小參數,所生成的BlockingQueue的大小由Integer.MAX_VALUE來決定.其所含的對象是以FIFO(先入先出)順序排序的
??????? 3)PriorityBlockingQueue:類似于LinkedBlockQueue,但其所含對象的排序不是FIFO,而是依據對象的自然排序順序或者是構造函數的Comparator決定的順序.
??????? 4)SynchronousQueue:特殊的BlockingQueue,對其的操作必須是放和取交替完成的.
??? 3.LinkedBlockingQueue和ArrayBlockingQueue比較起來,它們背后所用的數據結構不一樣,導致LinkedBlockingQueue的數據吞吐量要大于ArrayBlockingQueue,但在線程數量很大時其性能的可預見性低于ArrayBlockingQueue.??? ?????
?*/
public class BlockingQueueTest {
?????? /**定義裝蘋果的籃子*/
?????? public static class Basket{
?????? ?????? //籃子,能夠容納3個蘋果
?????? ?????? BlockingQueue<String> basket = new ArrayBlockingQueue<String>(3);
?????? ?????? //生產蘋果,放入籃子
?????? ?????? public void produce() throws InterruptedException{
?????? ?????? ?????? //put方法放入一個蘋果,若basket滿了,等到basket有位置
?????? ?????? ?????? basket.put("An apple");
?????? ?????? }
?????? ?????? //消費蘋果,從籃子中取走
?????? ?????? public String consume() throws InterruptedException{
?????? ?????? ?????? //take方法取出一個蘋果,若basket為空,等到basket有蘋果為止
?????? ?????? ?????? return basket.take();
?????? ?????? }
?????? }
?????? //測試方法
?????? public static void testBasket(){
?????? ?????? final Basket basket = new Basket();//建立一個裝蘋果的籃子
?????? ?????? //定義蘋果生產者
?????? ?????? class Producer implements Runnable{
?????? ?????? ?????? public void run(){
?????? ?????? ?????? ?????? try{
?????? ?????? ?????? ?????? ?????? while(true){
?????? ?????? ?????? ?????? ?????? ?????? //生產蘋果
?????? ?????? ?????? ?????? ?????? ?????? System.out.println("生產者準備生產蘋果: " + System.currentTimeMillis());
?????? ?????? ?????? ?????? ?????? ?????? basket.produce();
?????? ?????? ?????? ?????? ?????? ?????? System.out.println("生產者生產蘋果完畢: " + System.currentTimeMillis());
?????? ?????? ?????? ?????? ?????? ?????? //休眠300ms
?????? ?????? ?????? ?????? ?????? ?????? Thread.sleep(300);
?????? ?????? ?????? ?????? ?????? }
?????? ?????? ?????? ?????? }catch(InterruptedException ex){
?????? ?????? ?????? ?????? }
?????? ?????? ?????? }
?????? ?????? }
?????? ?????? //定義蘋果消費者
?????? ?????? class Consumer implements Runnable{
?????? ?????? ?????? public void run(){
?????? ?????? ?????? ?????? try{
?????? ?????? ?????? ?????? ?????? while(true){
?????? ?????? ?????? ?????? ?????? ?????? //消費蘋果
?????? ?????? ?????? ?????? ?????? ?????? System.out.println("消費者準備消費蘋果: " + System.currentTimeMillis());
?????? ?????? ?????? ?????? ?????? ?????? basket.consume();
?????? ?????? ?????? ?????? ?????? ?????? System.out.println("消費者消費蘋果完畢: " + System.currentTimeMillis());
?????? ?????? ?????? ?????? ?????? ?????? //休眠1000ms
?????? ?????? ?????? ?????? ?????? ?????? Thread.sleep(1000);
?????? ?????? ?????? ?????? ?????? }
?????? ?????? ?????? ?????? }catch(InterruptedException ex){
?????? ?????? ?????? ?????? }
?????? ?????? ?????? }
?????? ?????? }
?????? ?????? ExecutorService service = Executors.newCachedThreadPool();
?????? ?????? Producer producer = new Producer();
?????? ?????? Consumer consumer = new Consumer();
?????? ?????? service.submit(producer);
?????? ?????? service.submit(consumer);
?????? ?????? //程序運行5s后,所有任務停止
?????? ?????? try{
?????? ?????? ?????? Thread.sleep(5000);
?????? ?????? }catch(InterruptedException ex){
?????? ?????? }
?????? ?????? service.shutdownNow();
?????? }
?????? public static void main(String[] args){
?????? ?????? BlockingQueueTest.testBasket();
?????? }
}
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轉載于:https://www.cnblogs.com/likwo/archive/2010/07/01/1769199.html
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